Field of the Invention
The invention relates to a poly-V type of V-grooved sheet metal pulley for use in Poly-V Serpentine drive systems; and more particularly, to a new sheet metal poly-V pulley structure having roller spun cold-worked thickened groove-forming walls provided with a plurality of relatively narrow deep V-grooves formed in an axially extending pulley flange wall terminating in an outturned radial stiffening flange.
The invention relates further to a new combination of steps by which such a poly-V type V-grooved sheet metal pulley may be made to provide strong and thickened groove-forming walls in a one-piece cup-shaped sheet metal blank, and to provide an outturned radial stiffening flange at the open end of the cup for maintaining rigidity, stiffness, roundness, and parallelism of the poly-V grooved flange with the axis of the pulley when operating under heavily loaded drive conditions in a system containing a plurality of such pulleys as components.
Description of the Prior Art
The advent of Poly-V Serpentine drives which use a single poly-V belt to drive all of the under-the-hood-accessories in an automotive power unit, and which replaces a plurality of belts heretofore used to drive a fan, a water pump, an alternator, an air pump, power steering components, and air conditioning mechanisms, has called for strong, efficient and reliably operating poly-V pulley products.
Poly-V pulleys should have accurately formed V-grooves, dynamic pulley balance, and thick, rigid, strong and stable cold-worked metal in the poly-V groove pulley flange to provide the grooved flange with the necessary strength and rigidity for satisfactory and efficient operation of a poly-V drive system under heavy loading.
Prior poly-V pulleys, such as shown in U.S. Pat. No. 3,368,376, have had poly-V grooves formed with different angular contours on the inside and outside of the groove walls. Also, the metal in the groove walls has been formed by tension stretching and thinning which results in a weakened structure. In addition, the open end of the grooved pulley flange wall may not have sufficient rigidity and stiffness to prevent the pulley from becoming out of round under heavy loading, or to maintain parallelism between the grooved flange and the pulley axis during heavily loaded operation. This may result in inefficient driving contact between the pulley and the poly-V belt in a Poly-V Serpentine drive system.
Further, the manner in which the poly-V grooves are formed, as taught in said U.S. Pat. No. 3,368,376, produces groove-forming walls which are thinner than the parent metal in the pulley flange in which the grooves are formed; which are non-uniform in thickness because of a different inner and outer angular contour of the V-groove formations; and which inherently involve stretching the metal in the V-groove walls. These characteristics, which result from the manner in which the poly-V grooves are formed, all are undesirable. Thus, a new procedure for manufacturing poly-V pulleys which avoid the stated undesirable characteristics is a wanted concept.
Accordingly, there exists a need for a new poly-V pulley structure, and a method of making such a pulley, which provide increased strength and rigidity to the grooved pulley flange wall; thereby avoiding the inherent weaknesses present in prior poly-V pulleys, and avoiding the undesirable characteristics inherently present in prior pulleys resulting from the prior procedures used in the manufacture of such prior pulleys.